Charge air cooler arrangement with cooler bypass and method

ABSTRACT

A charge air cooler arrangement includes a first charge air cooler disposed upstream of an engine inlet, a second cooler disposed upstream of the first charge air cooler, and a bypass line for bypassing the second cooler, a downstream end of the bypass line being disposed upstream of the first charge air cooler. A method of reducing condensation in an engine having charge air cooling is also disclosed.

The present invention relates to a charge air cooling arrangement and,more particularly, a charge air cooling arrangement with a cooler bypassline.

As seen in FIG. 1A, which shows a conventional internal combustionengine 1, turbochargers or superchargers 2 compress incoming air,causing it to become heated. Because hot air is less dense than coolerair at the same pressure, the total charge delivered to the cylinders isless than it could be. By cooling the charge after compression usingdevices such as charge air coolers (CAC) 4 or, in multi-stageturbocharging systems, intercoolers, even more charge can be delivered,increasing power. Additionally, devices such as CACs and intercoolershelp to increase the total amount of boost allowable prior to thebeginning of detonation in the cylinder by decreasing the temperature ofthe air charge.

Exhaust gas recirculation (EGR) is a NOx (nitrogen oxide and nitrogendioxide) reduction technique used in most gasoline and diesel engines.EGR works by recirculating some percentage (e.g., 5-10%) of an engine'sexhaust gas back to the engine cylinders. Intermixing the incoming airwith recirculated exhaust gas dilutes the mix with inert gas which slowsthe combustion, and lowers the peak temperatures. Because NOx formationprogresses much faster at high temperatures, EGR serves to limit thegeneration of NOx. NOx is primarily formed due to the presence of oxygenand high temperatures.

Recirculation of exhaust gas is usually achieved by piping a route 5from the exhaust manifold 6 to the inlet manifold 7. A control valve 8(EGR valve) within the circuit regulates and times the gas flow. Inmodern diesel engines, the EGR gas is typically cooled using a heatexchanger (EGR cooler) 9 to allow the introduction of a greater mass ofrecirculated gas.

When devices such as CACs 4 cool charge air to temperatures below thedew point of the charge air, the resulting condensation, particularlywhen mixed with exhaust gases, can be harmful to engine parts such asinlet valves and inlet valve seats. One prior solution includes shuttingoff EGR when temperature of charge air exiting the CAC falls below thedew point temperature. Because this solution increases NOx formation, itis not approved by the U.S. Environmental Protection Agency.

Another prior solution includes directing some of the charge air througha bypass 10. However, when only a portion of the charge air bypasses theCAC 4, even though the mixture of charge air that has bypassed the CACand the charge air that has passed through the CAC may be at atemperature above the dew point as seen at point A in the graph of FIG.1B, charge air that passes through the CAC can still be cooled totemperatures below the dew point as seen at point B. Thus, the CACbypass 10 does not fully solve the problem of condensation.

According to an aspect of the present invention, an engine with a chargeair cooler arrangement comprises an engine, an inlet leading to theengine, a first charge air cooler disposed upstream of the inlet, asecond cooler disposed upstream of the first charge air cooler, and abypass line for bypassing the second cooler upstream of the first chargeair cooler.

According to another aspect of the present invention, a charge aircooler arrangement comprises a first charge air cooler disposed upstreamof an engine inlet, a second cooler disposed upstream of the firstcharge air cooler, and a bypass line for bypassing the second cooler, adownstream end of the bypass line being disposed upstream of the firstcharge air cooler.

According to yet another aspect of the present invention, a method ofreducing condensation in an engine having charge air cooling comprisescausing inlet air to flow through a first charge air cooler downstreamfrom a second cooler and a bypass line arranged for bypassing the secondcooler, and adjusting inlet air temperature downstream of the firstcharge air cooler by adjusting an amount of inlet air flow through thesecond cooler and the bypass line.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understoodby reading the following detailed description in conjunction with thedrawings in which like numerals indicate similar elements and in which:

FIG. 1A schematically shows a prior art engine with CAC, CAC bypass andEGR, and FIG. 1B is a graph of charge air temperature through a CAC andbypass of the type shown in FIG. 1A;

FIG. 2A schematically shows an engine with CAC according to anembodiment of the present invention, and FIG. 2B is a graph of chargeair temperature through a CAC and bypass of the type shown in FIG. 2A;and

FIG. 3 schematically shows an engine with CAC according to anotherembodiment of the present invention.

DETAILED DESCRIPTION

An engine 21 with a charge air cooler arrangement 23 is seen in FIG. 2A.An inlet, typically an inlet manifold 25, leads to the engine 21. Afirst charge air cooler 27 (CAC) is disposed upstream of the inletmanifold 25. The first CAC 27 may be less efficient than CACs typicallyused with conventional internal combustion engines. More particularly,it is desirable that the first CAC 27 be insufficiently efficient to beable to cool air in the range of temperatures and relative humidity inwhich the engine 21 is expected to be operated to a temperature belowthe dew point for the air in or downstream of the first CAC. In otherwords, the first CAC 27 will not ordinarily be able to causecondensation downstream of the first CAC.

A second cooler 29 is disposed upstream of the first CAC 27. It isdesirable that the second cooler 29 and the first CAC 27, operated inseries, be capable of lowering the temperature of inlet air in the rangeof temperature and relative humidity in which the engine 21 is expectedto be operated to temperatures substantially below the temperature atwhich the first CAC 27 is capable of lowering the temperature by itself.The first CAC 27 and the second cooler 29 operated in series may becapable of lowering inlet air temperatures to temperatures at or belowthe dew point of the inlet air.

A bypass line 31 is provided for bypassing the second cooler 29 upstreamof the first CAC 27. A downstream end 33 of the bypass line 31 is inflow communication with a conduit 35 between the first CAC 27 and thesecond cooler 29. When inlet air flows through the bypass line 31, thefirst CAC 27 does not cool the air to temperatures as low as it might ifall inlet air flowed through the second cooler 29.

An EGR circuit 37 can be in flow communication with the inlet manifold25. It is desirable that inlet air temperatures downstream of the firstCAC 27 be sufficiently high to avoid condensation as condensation,particularly together with EGR gases, tends to result in productsharmful to engine parts such as inlet valves and valve seats. Thetemperature of the inlet air downstream of the first CAC 27 can bemaintained at or above desired temperatures by shutting off flow throughthe second cooler 29 and directing all flow through the bypass line 31,or by appropriately balancing an amount of air that passes through thesecond cooler and an amount that flows through the bypass line.

An appropriate balance of inlet air through the second cooler 29 andinlet air through the bypass line 31 may be achieved using a valvearrangement 39 adapted to adjust flow of inlet air through the secondcooler and the bypass line. The valve arrangement 39 may be adapted toentirely shut off flow through the bypass line 31 and/or through thesecond cooler 29 or may be adapted to permit flow at desired levelsthrough both the second cooler and the bypass line. FIG. 2A shows avalve arrangement comprising valves 41 and 43 for adjusting flow throughthe second cooler 29 and the bypass line 31, respectively. The valves 41and 43 can have only open/closed modes or can be adjustable to variousstates between fully open or fully closed. Other valve arrangements willalso ordinarily be available, such as a three-way valve for permittingflow to only one of the second cooler 29 and the bypass line 31. FIG. 2Bis a graph showing that, as inlet air passes through the system, bypassing some inlet air through the second cooler 29 so that it is cooled(exiting the second cooler at point C) and some inlet air through thebypass line 31 so that it is not cooled, when those two streams arecombined (at point D) and then passed through the first CAC 27, thetemperature of the resulting, cooled stream (point E) can be maintainedabove a dew point temperature.

A sensor arrangement comprising a sensor adapted to sense datapertaining to a dew point of inlet air and adapted to send a signalrelating to the data to a controller 49 to control the valve arrangement39 in response to the signal can be provided. Data pertaining to the dewpoint of inlet air will ordinarily comprise one or more of inlet airtemperature and/or relative humidity upstream of the first CAC 27 andthe second cooler 29, inlet air temperature and/or relative humidityupstream of the first CAC and downstream of the second cooler, and inletair temperature and/or relative humidity downstream of the first CAC andthe second cooler. Such data can be collected by temperature and/orrelative humidity sensors 471 and 472 upstream of the first CAC 27 andthe second cooler 29, respectively; temperature and/or relative humiditysensors 473 and 474 upstream of the first CAC and downstream of thesecond cooler, respectively; and temperature and/or relative humiditysensors 475 and 476 downstream of the first CAC and the second cooler,respectively. Thus, the sensor arrangement may comprise sensors such astemperature sensors (e.g., thermometers and temperature sensitiveswitches), humidity sensors or dew point sensors (such as hygrometers),and the like although, by listing the foregoing types of sensors, it isnot intended to limit the types of equipment that can be used todetermine or estimate a dew point of the inlet air.

The sensor arrangement may comprise a sensor in the form of atemperature sensor 475 adapted to monitor temperature downstream of thefirst CAC 27 and send a signal relating to the temperature to thecontroller 49 to control the valve arrangement 39 in response to thesignal. The controller 49 can be arranged to adjust the valvearrangement 39 in response to signals that the temperature downstream ofthe first CAC 27 is below a dew point temperature of the inlet air sothat flow through the second cooler 29 is reduced and flow through thebypass line 31 is increased. The signals may be based on measurements ofother factors, such as pressure, relative humidity, and temperatureupstream and downstream of the first CAC 27 and the second cooler 29that can be used to calculate whether conditions for condensation existdownstream of the first CAC, or they may be based solely on measurementof a single parameter, e.g., temperature at some point (such asdownstream of the first CAC) at which it is anticipated that undertypical operating conditions there will often be condensation downstreamof the first CAC. When monitored/sensed conditions are such thatcondensation downstream of the first CAC 27 is anticipated, the bypass31 can be opened and/or the second cooler 29 can be closed so thatconditions downstream of the first CAC 27 are unlikely to result incondensation.

The EGR circuit 37 will typically be in communication with the inlet 25.The EGR circuit 37 includes an EGR valve 53 responsive to a signal fromthe sensor arrangement to open and shut the EGR valve. The EGR valve 53may, for example, be shut in response to a signal from the temperaturesensor 475 downstream of the first CAC 27 reflecting conditions likelyto result in condensation. The temperature sensor 475 can send a signalto the controller 49 which, in turn, sends a signal to the EGR valve.The EGR circuit 37 also includes an EGR cooler 55 and other componentsof conventional EGR systems and can be operated in substantially thesame way as a conventional EGR system.

The second cooler 29 can be a cooler of any suitable type. Typically,the second cooler will be a CAC downstream of a turbocharger 57 orsupercharger as seen in FIG. 2A or, as seen in FIG. 3, the second cooler129 can be, e.g., an intercooler downstream of a first turbocharger 57and upstream of a second turbocharger 157 of a two-stage turbochargingsystem.

In a method of reducing condensation in an engine 21 having the chargeair cooling arrangement 23, inlet air is caused to flow through thefirst CAC 27 downstream from the second cooler 29 and downstream fromthe bypass line 31 arranged for bypassing the second cooler. Inlet airtemperature downstream of the first CAC 27 is adjusted by adjusting anamount of inlet air flow through the second cooler 29 and the bypassline 31. The amount of inlet air flow through the second cooler 29 andthe bypass line 31 can be adjusted in any suitable fashion, such as byshutting one line and opening the other, or by partially opening orclosing one or both lines so as to achieve a desired temperaturedownstream of the first CAC 27.

Typically, inlet air temperature will be monitored and the amount ofinlet air flow through the second cooler 29 and the bypass line 31 willbe adjusted as a function of inlet air temperature. For example, when asensor such as the temperature sensor 475 determines that thetemperature downstream of the first CAC 27 has dropped to a level near,at, or below a temperature at which condensation is expected to occur,the volume of flow through the second cooler 29 can be decreased and thevolume of flow through the bypass can be increased. In addition tomonitoring inlet air temperature downstream of the first CAC 27, inletair temperature can be monitored upstream of the first CAC, such as bysensors 471 and/or 473. Further, parameters other than temperature maybe monitored, and the amount of flow through the second cooler 29 andthe bypass line 31 can be controlled as a function of those parametersalone or in combination with other parameters.

In the present application, the use of terms such as “including” isopen-ended and is intended to have the same meaning as terms such as“comprising” and not preclude the presence of other structure, material,or acts. Similarly, though the use of terms such as “can” or “may” isintended to be open-ended and to reflect that structure, material, oracts are not necessary, the failure to use such terms is not intended toreflect that structure, material, or acts are essential. To the extentthat structure, material, or acts are presently considered to beessential, they are identified as such.

While this invention has been illustrated and described in accordancewith a preferred embodiment, it is recognized that variations andchanges may be made therein without departing from the invention as setforth in the claims.

1. An engine with a charge air cooler arrangement, comprising: anengine; an inlet leading to the engine; a first charge air coolerdisposed upstream of the inlet; a second cooler disposed upstream of thefirst charge air cooler; a bypass line for bypassing the second coolerupstream of the first charge air cooler; a valve arrangement adapted toadjust flow of inlet air through the second cooler and the bypass line;and a sensor arrangement comprising a sensor adapted to sense datapertaining to a dew point of inlet air and send a signal relating to thedata to a controller to control the valve arrangement in response to thesignal.
 2. The engine with a charge air cooler arrangement as set forthin claim 1, comprising an EGR circuit in communication with the inlet.3. The engine with a charge air cooler arrangement as set forth in claim1, wherein the valve arrangement is adapted to shut off flow through thebypass line.
 4. The engine with a charge air cooler arrangement as setforth in claim 3, wherein the valve arrangement is adapted to shut offflow through the second cooler.
 5. The engine with a charge air coolerarrangement as set forth in claim 1, wherein the valve arrangement isadapted to shut off flow through the second cooler.
 6. The engine with acharge air cooler arrangement as set forth in claim 1, wherein the,valve arrangement is adapted to permit flow through both the secondcooler and the bypass line.
 7. The engine with a charge air coolerarrangement as set forth in claim 1, wherein the sensor arrangementcomprises a temperature sensor adapted to monitor temperature downstreamof the first charge air cooler and send a signal relating to thetemperature to the controller to control the valve arrangement inresponse to the signal.
 8. The engine with a charge air coolerarrangement as set forth in claim 7, wherein the controller is arrangedto adjust the valve arrangement in response to signals that thetemperature downstream of the first charge air cooler is below a dewpoint of the inlet air so that flow through the second cooler is reducedand flow through the bypass line is increased.
 9. The engine with acharge air cooler arrangement as set forth in claim 1, comprising an EGRcircuit in communication with the inlet, the EGR circuit including anEGR valve responsive to a signal from the sensor arrangement to open andshut the EGR valve.
 10. The engine with a charge air cooler arrangementas set forth in claim 1, comprising a sensor arrangement comprising atemperature sensor adapted to monitor temperature downstream of thefirst charge air cooler and send a signal relating to the temperature toa controller to control the valve arrangement in response to the signal.11. The engine with a charge air cooler arrangement as set forth inclaim 1 wherein the second cooler is a charge air cooler.
 12. The enginewith a charge air cooler arrangement as set forth in claim 1, whereinthe second cooler is an intercooler downstream of a first turbochargerand upstream of a second turbocharger of a two-stage turbochargingsystem.
 13. A charge air cooler arrangement, comprising: a first chargeair cooler disposed upstream of an engine inlet; a second coolerdisposed upstream of the first charge air cooler; a bypass line forbypassing the second cooler, a downstream end of the bypass line beingdisposed upstream of the first charge air cooler; a valve arrangementadapted to adjust flow of inlet air through the second cooler and thebypass line; and a sensor arrangement comprising a sensor adapted tosense data pertaining to a dew point of inlet air and send a signalrelating to the data to a controller to control the valve arrangement inresponse to the signal.
 14. The charge air cooler arrangement as setforth in claim 13, wherein the sensor arrangement comprises atemperature sensor adapted to monitor temperature downstream of thefirst charge air cooler and send a signal relating to the temperature tothe controller to control the valve arrangement in response to thesignal.
 15. The charge air cooler arrangement as set forth in claim 14,wherein the controller is arranged to adjust the valve arrangement inresponse to signals that the temperature downstream of the first chargeair cooler is below a dew point of the inlet air so that flow throughthe second cooler is reduced and flow through tee bypass line isincreased.
 16. The charge air cooler arrangement as set forth in claim13, comprising a sensor arrangement comprising a temperature sensoradapted to monitor temperature downstream of the first charge air coolerand send a signal relating to the temperature to a controller to controlthe valve arrangement in response to the signal.
 17. A method ofreducing condensation in an engine having charge air cooling,comprising: causing inlet air to flow through a first charge air coolerdownstream from a second cooler and a bypass line arranged for bypassingthe second cooler; and adjusting inlet air temperature downstream of thefirst charge air cooler by adjusting an amount of inlet air flow throughthe second cooler and the bypass line; and monitoring inlet airtemperature and adjusting the amount of inlet air flow through thesecond cooler and the bypass line as a function of inlet airtemperature.
 18. The method of reducing condensation in an engine havingcharge air cooling as set forth in claim 17, wherein inlet airtemperature is monitored upstream of the first charge air cooler. 19.The method of reducing condensation in an engine having charge aircooling as set forth in claim 17, wherein inlet air temperature ismonitored downstream of the first charge air cooler.
 20. The method ofreducing condensation in an engine having charge air cooling as setforth in claim 17, wherein air temperature is also monitored upstream ofthe first charge air cooler.